LONDON — The two assassins sent to southwest England in March to poison a Russian former spy were active officers in Russia’s military intelligence, Prime Minister Theresa May of Britain said on Wednesday, after prosecutors accused the men of attempted murder, the first criminal charges in a case that has driven a deep wedge between Russia and the West.

Investigators released a cache of evidence in the case, including security camera images that captured the progress of two husky men from an Aeroflot flight to the scene of the crime, near the victim’s home, and from there back to Moscow.

They also released photographs of the delicate perfume bottle that was used to carry a weapons-grade nerve agent, known as Novichok, to the quiet English cathedral city of Salisbury.

British counterterrorism police said at a news conference that they had pored through thousands of hours of security-camera footage, cross-referenced the results with passport data, and on May 2, identified a shabby hotel in East London where the men had stayed. Finally, in a needle-in-a-haystack moment, two swabs taken from the suspects’ hotel were found to contain traces of the nerve agent.

“This was not a rogue operation,” she said. “It was almost certainly also approved outside the G.R.U. at a senior level of the Russian state.”

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British investigators used security footage and flight records to track two Russian men who now stand accused of attempted murder in the March attack featuring the nerve agent Novichok.CreditCreditBritish Metropolitan Police

She said the nerve agent attacks were of a piece with a long string of Russian operations spearheaded by the G.R.U., including the seizure of Crimea, incursions into eastern Ukraine, the downing of a civilian airliner in Ukrainian airspace, and an attempted coup in Montenegro.

The allegation of specific G.R.U. involvement in the use of the nerve agent adds to the heightened tensions between Moscow and the West, which has led to mutual expulsions of hundreds of diplomats and embassy employees, and to sanctions against Russia.

The British authorities issued domestic and European arrest warrants for the two men, identified as Alexander Petrov and Ruslan Boshirov, and released photographs of them. The men traveled on valid Russian passports on those names, the police said, adding that they believed the names were aliases.

“We do understand they have traveled extensively in the past under these aliases,” Neil Basu, Britain’s top counterterrorism police official, said.

The information released on Wednesday made clear that investigators had known of the men’s assumed names, their movements and the contamination of their hotel room for months without saying so publicly. On Wednesday, they appealed for the public’s help to fill in the gaps about what the men had done, and when.

“The names, as well as the photos, published in the media mean nothing to us,” Maria Zakharova, a spokeswoman for the Russian Foreign Ministry, told journalists on Wednesday. “We once again urge the U.K. to switch from public accusations and informational manipulations to practical interaction between law enforcement agencies.”

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Sergei V. Skripal at a court hearing in Moscow in 2006. He was released in 2010 as part of a spy swap with Western countries.CreditMoscow District Military Court, via Getty Images

The Crown Prosecution Service charged the men with the attempted murder of the Russian former intelligence officer, Sergei V. Skripal; of Yulia S. Skripal, his daughter; and of a police officer, Det. Sgt. Nick Bailey, who was sickened while investigating the case. The men were also charged with conspiracy to murder Mr. Skripal; use and possession of the nerve agent; and causing grievous bodily harm.

The charges do not address the poisoning of two Britons — Dawn Sturgess, who died, and Charlie Rowley — though investigators believe the events are linked. Both Ms. Sturgess and Mr. Rowley fell ill months after the attack on the Skripals, when they found the perfume bottle that investigators believe was used to transport the nerve agent.

“The same two men are now the prime suspects in the case of Dawn Sturgess and Charlie Rowley,” Mrs. May said, adding that the same poison was used in both cases and that the two were “victims of the reckless disposal of this agent.”

Prosecutors did not request the extradition of the men from Russia, which does not send its nationals abroad for prosecution. Mr. Basu said that, while he hoped for arrests, “it’s looking very very unlikely that we are going to get to that point.”

The images released by the police show how easily the attack could have escaped detection. The suspects look perfectly ordinary, strolling in wintry weather in jeans and parkas. The police released pictures of the counterfeit bottle for a perfume, Nina Ricci’s Premier Jour, and a pearlescent pink box that contained it — a container so innocuous that Mr. Basu called it “the perfect delivery method.”

Mrs. May said, “the manner in which the bottle was modified leaves no doubt, it was a cover for smuggling a weapon into the country.”

All five victims were poisoned with Novichok, a class of nerve agents developed by Soviet and Russian scientists, according to British government scientists and the Organization for the Prohibition of Chemical Weapons, the international agency that monitors compliance with a global treaty on chemical weapons.

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Mr. Skripal’s daughter, Yulia, was also poisoned, but may have been an unintended victim.CreditDylan Martinez/Agence France-Presse — Getty Images

Britain won backing from its Western allies for the conclusion that Moscow was behind the attack, touching off the latest in a series of diplomatic breaches between the Kremlin and the West.

After the attack on the Skripals in Salisbury, a cathedral city southwest of London, Western nations imposed new economic sanctions and expelled about 150 Russian diplomats and other officials, many of them believed to be intelligence agents. Russia responded by ejecting a similar number of officials from those countries.

Mr. Basu said the suspects were in Britain only briefly, flying in from Moscow on March 2, staying for two nights at the City Stay Hotel on Bow Road in East London, and flying back to Moscow on March 4. The dusty, low-cost hotel, with a patch of artificial grass in front, is next to a train station.

After tracing the men’s movements to the hotel and determining which room they stayed in, Mr. Basu said, investigators examined the room on May 4 and “two swabs showed contamination of Novichok at levels below that which would cause concern for public health.”

People who live and work in the area said they were dismayed not to have heard of the contamination earlier. “It’s a bit shocking that they waited until now, but I guess there’s a lot that goes on behind the scenes that I’m not aware of,” said Andreia Paim, 24, a student who lives near the hotel.

The men took a train to Salisbury on March 3, Mr. Basu said, adding that the trip “was for reconnaissance of the Salisbury area.” He said they had returned the next day to carry out the poisoning. The police said closed-circuit television recordings showed the men near, but not at, Mr. Skripal’s house.

Mr. Skripal is believed to have been the primary target of the attack — he is apparently the latest in a long string of people at odds with President Vladimir V. Putin’s government who have been the victims of assassinations or attempted assassinations, in Russia and abroad.

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Dawn Sturgess and Charles Rowley. They were poisoned three months after the attack on the Skripals, and Ms. Sturgess later died.CreditAgence France-Presse — Getty Images

The Skripals fell seriously ill on March 4 with what was diagnosed within days as nerve agent poisoning, leading to a lockdown of parts of Salisbury and terrifying residents, as hundreds of workers in hazardous materials suits searched for contamination. Doctors did not expect them to survive, but the Skripals, who were found unresponsive in a Salisbury park, were released from a hospital after weeks of treatment.

Investigators concluded that the poison had been applied to the front door of Mr. Skripal’s house in Salisbury; his daughter, Yulia, who was visiting from Russia, may have been an unintended victim. A police officer who took part in the initial investigation was sickened by the same substance but has recovered.

On June 30, two Britons were poisoned with what investigators said was the same nerve agent — Ms. Sturgess, who lived in Salisbury, and her boyfriend, Mr. Rowley, who lived nearby, in Amesbury. Ms. Sturgess died eight days later, turning the investigation into a murder case.

Once again, Salisbury was upended by a search for more contamination, prompting a new wave of fear among residents, who complained that officials’ assurances of relative safety had been meaningless.

Mr. Rowley said he and Ms. Sturgess had become sick after handling the perfume bottle, which he had found. The authorities have said the bottle contained the toxin and had apparently been discarded by the person or persons who had carried out the attack on the Skripals.